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Re: Why is a hash the default "object" in oo perl?

by tinita (Parson)
on Jul 18, 2004 at 01:51 UTC ( #375309=note: print w/ replies, xml ) Need Help??


in reply to Why is a hash the default "object" in oo perl?

hmm, i thought about that and made up some code, just for fun.
i don't know if it's really useful and correct, but it was interesting to think about, so i'm just posting this here.
we're talking just about the object-attributes and the get/set methods, i assume.
so, when i create a class i usually find myself defining an attribute method like:

sub _attr { my $self = shift; my $name = shift; return $self->{"_$name"} unless @_; $self->{"_$name"} = shift; } sub name { shift->_attr(name => @_); }

so that you can call $obj->name("new name");
(I know i could actually use Class::MethodMaker or something similar...)

now how could we make that more generic?
i thought about defining a pragma 'attribute' that you can use like that:

package Parent; use attribute sub { my $self = shift; my $name = shift; # we have an ordinary hashref for the object return \$self->{"_$name"}; }, [qw(city name)];
package Child; use base 'Parent'; use attribute sub { my $self = shift; my $name = shift; # object is arrayref, and the attributes are stored in element 0 return \$self->[0]->{"_$name"}; };

so with that, and the assumption that the module you inherit always uses methods to get/set attributes, you are independent from the implementation, right? here's attribute.pm:
package attribute; use strict; use warnings; sub import { my ($self, $sub, $names) = @_; my $class = caller(); no strict 'refs'; # set the general method *{$class . '::_attribute_ref' } = $sub; for my $name (@$names) { my $string = $class . '::' . $name; *{$string} = sub { my $self = shift; # set method for each attribute return ${ $self->_attribute_ref($name) } unless @_; ${ $self->_attribute_ref($name) } = shift; }; } } 1;
update: changed subname '_attribute_set' to '_attribute_ref'
moved readmore tag a little


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